Port forwarding is not required, try this first:
From the main menu click "Tournaments", then "Host Tournament", then select a level (good 2-player maps are Beach, Lurk, Bats, Octogame, Smores, Sky, Below, Chill, Gajoob, Circle, Crossover) and click "Start Level". You should get a message that your server has been publicly listed.
Your friend then clicks on "Tournaments" from the main menu, then "Find Tournament" and selects your server.

If the above doesn't work ensure that "Public" is checked on the "Host Tournament" screen. If you want to limit so that only your buddy can join then set "Connections" to 2 on the "Host Tournament" screen. If your friend cannot connect then you can setup port forwarding using the info here: http://clonesgame.com/port-forward